1. Field of the Invention
This invention relates to auto-reclosers.
2. Description of Related Art
A pole mounted auto-recloser is a high voltage pole-top mounted reclosing circuit-breaker which is used to protect high voltage overhead electrical power distribution lines. The function of the recloser is to reduce system interruption to a minimum if a transient or permanent fault should occur on the system. The recloser senses fault current in the main HV circuit, that is in the three phase power line, and opens its three main contacts to interrupt the current. After a short period known as the dead-time the recloser will reclose. Most faults are transient in nature and will clear during the dead-time so that when the unit recloses the HV supply is restored. If the fault has not cleared the recloser senses the fault current and again opens to interrupt it. The recloser can attempt to reclose up to say three times. If the fault is permanent after a predetermined number of trips it will remain open thereby isolating the faulty section of line.
An inherent problem with pole mounted reclosers is that such equipment is typically situated in remote locations. For this reason they have to be very reliable with very long intervals between maintenance periods. Also there will be no local power supply for opening and closing the recloser main contacts or for supplying the electronic protection and control unit part of the recloser.
There are many solutions to the problem of power supply all of which have involved obtaining power either directly or indirectly from the HV supply. This presents problems when one considers the fact that there will be a fault on the HV supply at the very moment when the HV supply is required to operate the recloser; also it is not possible to close the recloser if there is no HV supply.